A Two-Dimensional Diabatic Isopycnal Model Of A Coastal Upwelling Front

Date of Award




Degree Name

Doctor of Philosophy (Ph.D.)


Meteorology and Physical Oceanography


A two-dimensional high resolution diabatic isopycnal model is designed to simulate coastal upwelling frontogenesis under favorable longshore wind stress. Diabatic effects are generated by vertical mixing of density. The vertical eddy coefficients are determined explicitly from the mean field gradient by either a Richardson number related formula or a second order moment closure turbulence model. Munk & Anderson's empirical formula is chosen for the first method. For the second method, a simplified diagnostic version of a turbulence closure model derived from Worthem & Mellor's model (in press) is used.Several aspects of coastal upwelling dynamics, such as large scale divergent adjustment, side-wall friction and topographic effects, were studied for various simulated conditions.This study suggests that there is a strong interaction between the turbulent mixing and the frontal structure. Certain phenomena on the frontal scale emerge from all the case studies. Two phenomena are particularly important: First, the velocity and density structure of the front confine the turbulence events to localized regions; Second, these localized turbulent events largely affect the frontal structure and secondary circulation on the frontal scale. A double cell circulation is found in the model simulation.The vertical turbulent mixing in a frontal region has more complicated effects than a simple downward diffusion of heat and momentum. Changing the density and momentum profiles in a water column affects the horizontal density and momentum gradients for the surrounding area. Thus, the frontal scale secondary circulation is affected.It is this secondary circulation pattern which induces concentrated upwelling flow away from the coast. This flow may be important in increasing localized nutrient concentration and inducing patches of high biological productivity water.


Physical Oceanography

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